Utilizing a non-dedicated mini-computer developed during the first year of grant support, on-line analysis of 133-Xenon ventilatory and perfusion lung scans will be carried out in patients with various forms of chronic obstructive pulmonary disease. In addition to several unique analytical techniques developed for the scans themselves, routine pulmonary function testing is employed so that correlations may be developed with the digitally analyzed scan data. Current computer evaluation of scan data includes: isometric plotting in four views, shades-of-gray plotting, inertial moment analysis and iso-density plotting. Addition of perfusion scanning with saline-equilibrated 133- Xenon will permit extension of these techniques to ventilation/perfusion relationships. A primary avenue of investigation during the coming grant year will be analysis of Xenon washout time constants and correlation with breath-by-breath, on-line nitrogen washout curves.